Death associated protein kinase 1 (DAPK1) mediates cellular death after neuronal injury. An essential function of DAPK1 in acute neuronal death is its binding to the GluN2B subunit of the N-methyl-D-aspartate type glutamate receptor (NMDAR) and phosphorylation of serine 1303 of GluN2B. Phosphorylation of this site results in increased NMDAR conductance and neurotoxic increases in intracellular Ca2+ influx. Importantly, disrupting DAPK1 activity or DAPK1/GluN2B binding in several models of neuronal injury results in attenuated cell death. Despite this, the regulation of DAPK1 binding to GluN2B remains completely unexplored. Pathological activation of DAPK1 occurs in an NMDAR and calcineurin (CaN) dependent manner. The NMDAR also plays a particularly important role in synaptic plasticity, and its activation is required for synaptic long-term potentiation (LTP) as well as som forms of long-term depression (LTD) in the hippocampus. Additionally, LTD also requires CaN activation, suggesting that DAPK1 may also be activated during physiological synaptic plasticity. Aim 1: To determine the regulatory mechanisms of DAPK1/GluN2B binding in vitro and in cells. Aim1.1: To test the hypothesis that DAPK1 binding to GluN2B is regulated by Ca2+/calmodulin and phosphorylation state. The specific regulation of DAPK1 binding to GluN2B will be examined in vitro and in cells using DAPK1 mutants that mimic different phosphorylation and activation states. Aim 1.2: To test the hypothesis that DAPK1 translocation to excitatory synapses is induced by LTD and excitotoxicity, but not LTP. DAPK1 targeting to excitatory synapses will be examined in dissociated hippocampal neurons during stimuli eliciting LTD, LTP, or excitotoxicity. Aim 2: To determine the role of DAPK1 in synaptic plasticity. Aim 2.1: To test the hypothesis that DAPK1 is activated in a CaN dependent manner during LTD. Slice biochemical studies will be used to investigate if DAPK1 is activated during LTD, the activating phosphatase(s), and whether a downstream effector of DAPK1 is affected. Aim 2.2: To test the hypothesis that DAPK1 activity and the DAPK1/GluN2B interaction are necessary for the induction of LTD. The functional effects of DAPK1 and the DAPK1/GluN2B interaction will be investigated in mouse hippocampal slices using electrophysiological recordings and slice biochemistry. A combination of pharmacological DAPK1 inhibitors and two mutant mice will be used to examine the function of DAPK1 in synaptic plasticity. The results of this proposal will establish the regulatory mechanisms underlying the DAPK1/GluN2B interaction that promotes neuronal cell death after glutamate insults during stroke or traumatic brain injury. Additionally, novel role for DAPK1 in synaptic plasticity will be examined.